Compressor unloading device



Dec. 22, 1936. B. s. AIKMAN COMPRESSOR UNLOADING DEVICE- Filed Jan. 50, 1935 2 Sheets-Sheet 1 INVENTO'R BURTON 5. AIKMAN.

NEY

ATTOR Dec. 22, 1936.

B s. AIKMAN CCMPRES SOR UNLOADING DEVICE} Filed Jan. 30, 1955 2, Sheets-Sheet -2 m T N E V m BURTON, 5. AI KMANj BY 9%.

- A'ITOR NEY the compressor.

Patented Dec. 22 1936 UNITED STATES PATENT OFFICE I 2.005.204 comnassoa momma navrca Burton S. Aikman, Wilkinsburg, Pa., assignor'to The Westinghouse Air Brake Compa y, Wilmerding, Pa, a corporation of Pennsylvania Application January 30,1935, Serial No. 4,042

21 Claims. (01. 230-206) This invention relates to fluid compressors and particularly to control mechanism for. continuously driven compressors and adapted to pro- 'tect the compressor against trouble in the event of failure of the lubricating system.

In many installations fluid compressors are,

continuously driven by means ,of an internal combustion engine or asynchronous motor, or otherwise, and the compressor is provided with means to hold the inlet valve open to unload the compressor when the pressure 0! the fluid compressed by the compressor. exceeds a predetermined value.

Compressors as 'now constructed frequently are provided with an oil reservoir in the lower porparticularly if it were permitted to operate under load, that is, to compress fluid at a time when it was not,properly lubricated. It is desirable,

therefore, to provide means to unload the compressor in the event of failure of the lubricating system for any reason. t

It is an object of this invention to provide an improved compressor unloading device operable in response to variations in the pressure of the fluid compressed by the compressor and to the .pressure of the liquid in the lubricating system.

A further object of the'invention is to provide an improved compressor. unloading system.

Another object of the invention is to provide a compressor having an inlet valve provided with in either the pressure of the fluid in the reservoir. associated with the compressor or the pressure of the liquid in the lubricating system.

A further object of the invention is to provide I g supplied to the chamber 30 through the pipe and a compressor with an inlet valve having unloading means operated by fluid under pressure irom the reservoir associated with the compressor and having valve means controlling the supply of fluid under pressure to the unloading means, this valve means being operable inresponse to variations in the pressure of the fluid in the reseryou or to variations in the pressure of the fluid inthe lubricating system.

A further object of the invention is to provide a an improved control device for use with a continuously operated compressor to control the volume oi air compressed by the compressor and to protect the compressor in the event of failure of the lubricating system.

Other objects 01 the invention and features of -bers into engagement with the seat'2l.

novelty will be apparent from the following description taken in connection with the accompanying drawings, in which Figure 1 is an elevational view of one embodiment of a compressor equipped with the control mechanism provided by my invention;

Figure 2 is an end view of the compressor shown in Figure l; and- Figure 3 is a diagrammatic view of a compressor equipped with the protective system provided by this invention.'

Referringto the drawings, I have illustrated one form of compressor equipped with the protective system'provided by my invention, and the compressor therein illustrated comprises a cylinder body indicated generally by the reference character 10 and having a pair of cylinders formed therein in which are reciprocable pistons l2 which are secured on the ends oi? connecting rods l3 which have their lower ends l5 secured on throws of the crankshaft ll. The crankshaft I! is supported on anti-friction bearings l8 whichare supported by the compressor body l0; Each of the cylinders II has an inlet valve assembly 20 associated therewith, and as is best shown in Figure 3 of the drawings, the inlet valve assembly comprises a valve seat 2| extending across a passage leading ,to the cylinder and having a pair of annular rings 22 and 23 which are adapted to engage the seat 2| and to close the passages 24 Springs 21 are provided whichengage the rings or discs 22 and 23 to normally urge these mem- The springs 21 are heldby a cage 28.

The valve assembly also. includes a piston chamber indicated at 3|! and having a piston 3| reciprocable therein. The piston 3| has a plurality of fingers 32 and 33 secured to the lower face thereof and extending into the passages 24 and 25 in the valve seat 2|, while aspring 35 is interposed between the piston 3| and the valve seat 2| and normally urges the piston upwardly as viewed in Figure 3. Fluid under pressure is passage ll, and on an increase is the pressure of the'fluid in the chamber 20 the piston: 3| is urged downwardly against'the spring 35 to press the fingers 32 and 33 against the rings 22 and-23' to unseat these members and unload the com-I is adapted to draw lubricant from the lower or crankcase portion of the cylinder body "which serves as an oil reservoir and force it through suitable passages to the connecting rod '30 and which extend through thevalve seat.

As shown in the drawings the pump 40 comprises a piston 4 I, which is .journaled on an eccentric 42 formed on the crankshaft I1 and is reciprocable in a piston chamber 43 formed in the member 44, which is pivotally mounted on the compressor body I0 by means of brackets 46 and 41. The piston 4| has a passage 50 extending therethrough and registering with an annular groove 5| formed in the eccentric 42 on the crankshaft I1, which in turn communicates with a passage 52 drilled in the crankshaft and leading to the throws of the crankshaft on which the connecting rods I3 are mounted.

The lower end of the passage 50 in the piston 4| is controlled by a check valve device, which, as shown in the drawings, comprises a seat 54 which has a ball valve element 55 engageable therewith to close the passage 56 extending therethrough. The ball valve element 55 is pressed to its seat by the'spring 51 so as to normally close the passage through the piston. The chamber 43 has an inlet passage 60 communicating therewith at a point spaced from the end thereof and leading from a chamber formed in the bracket piece 46, this chamber having a screen 6I- extending thereacross through which is drawn the oil which flows to the pump.

The chamber 43 has a discharge passage 65 leading therefrom at a point adjacent the end thereof and communicating with a pressure release valve element 66, which, as'shown in the drawings, comprises a seat 61 having a ball valve element 68 normally held in engagement therewith by means of a spring 69. When the pressure of the oil pumped by the pump exceeds a predetermined value, the ball valve element 68 is forced away from the seat to permit a portion of the oil to escape, thereby limiting the pressure which can be built up in the lubricating system. The passage 65 also hasa passage 10 communicating therewith, the flow of fluid from the passage 65 to the passage 10 -being controlled by means of a choke indicated at 1|, which serves to limit the rate of flow to the passage 10.

In the operation of the pump, the piston 4| reciprocates in the piston chamber 43 so that the end of the piston 4| at one point in its range of movement is located above the inlet passage 60 leading to the chamber 43 and at another point in its range of movement is'located below the passage 60. When the piston moves upwardly lubricant is sucked into the piston chamber 43, and when the piston 4| moves downwardly it cuts off the inlet passage 60 leading to the chamber 43, and the oil in the chamber is placed under pressure so that the ball valve 55 is unseated and a portion of the oil flows through the passage 50 to the annular groove 5 I, and therefrom through the passage 52 to the connecting rod bearings, while some of the oil flows through the passage 65 to the passage 10 which leads to the control valve. In the event that the pump pumps an'excess of oil over that required by the connecting rod bearings or the system so that in the event that there is a reduction in the pressure of the liquid supplied by the lubricating system, or an insufficient quantity of lubricant so supplied, this lubricant will be supplied to the compressor rather than to the control valve element because of the difference in the hydrostatic pressures which must be overcome to force oil to these parts.

As shown in the drawings the control valve device comprises a casing having a valve chamber indicated at 8| and communicating with the unloading valve 20 by means of the pipe 31.

The valve chamber 8| contains a double beat valve element 93 having seat portions 94 and 95, the seat portion 94 controlling communication between the valve chamber 8| and the chamber 86, which communicates through the passage and pipe 81 with the storage reservoir 88 into which the compressor compresses fluid. The seat portion controls communication. from the valve chamber 8| to a chamber which is connected to the crankcase chamber, and thus to the atmosphere by way of the passage 92.

The discharge end of the passage 92, in the.

has a chamber I00 therein which is connected to the passage 81 by way of the passage I 0| so that the chamber is supplied with fluid at. the pressure of fluid compressed by the compressor. The chamber I00 has a diaphragm I03 extending thereacross and subject to the pressure of the fluid in the chamber I00. A disc I05 engages one side of the diaphragm I 03 and hasa stem I01 secured thereto, while a plate'IIO is positioned against a face of the disc I05 and is slightly larger in diameter than the opening in the housing of the control valve device 80 in which the disc I05 operates. A compression spring III is fitted on the stem I01 and normally urges the disc I 05 to the left, as viewed in Figure 3, until the plate IIO engages the body of the control valve device 80. The plate IIO serves to limit the amount of deflection of the diaphragm I03 produced by the spring I i I.

The control valve device 80 .also has a piston chamber I20 formed therein and a piston I2I is provided which is reciprocable in this cylinder. The piston chamber I20 is connected to pipe and passage I23 leading to the passage 10 so that the piston I2I is subject on one side to the pressure created by the operation of the pump 40. The pressure of the fluid acting on the end of the piston I2I urges the piston to the left, as viewed in Figure 3, against the end of the valve element 93, urging it. to the left against the pressure of the spring 91 so as to press the valve seat portion 94 into engagement with the seat associated therewith to cut off communication betweenthe chamber 8| and the passage 81, and to open communication between the chamber 8| and the passage 92 leading to the atmosphere.

The passage I23 also communicates with a chamber I30, in which is'positioned a valve assembly indicated generally by the reference character I3I, and, which as shown, comprises a pis ton I32,'and a valve disc I33 adapted to, seat against a seat I34 formed in the housing of the control valve device 80. The piston I32 is normally urged to the left, as viewed in Figure 3,

by means of a spring I so that the valve disc I33 is in engagement with the seat I34. The

valve disc I33 is located axially in alignment with the pin I01, and the end of the pin I01 is closely adjacent the disc I33.

The valve disc I33 controls-communication bethe piston I2|, and therefrom to the passage 82 which leads to the atmosphere through the crankcase chamber of the compressor. A passage I44 also communicates with the passage HI and with the chamber I30 on the right hand side of the piston I32. I

The operation of the control valve device 80 is as follows. Assuming that the pressure of the fluid in the reservoir 88 is below a predetermined value, and assuming that the lubricating system is functioning properly to supply lubricant under pressure to the compressor and to the control valve device, the movable abutment or piston |2| is urged to the left, as viewed in Figure 3 3, to move the valve element 83 to a position in which the valve 8.4 is seated so that communication is closed off from chamber8| to passage IOI, which passage is connected to pipe and passage 81 leading to the storage reservoir 88, into which the compressor compresses fluid. At the same time the valve 85 is unseated so that the chamber 8| is open to the atmosphere by way of exhaust passage 82, so that the unloading means 20 associated with the inlet valve of the compressor is in communication with the atmos ton in to the right, as viewed in Figure 3, thereby closing the passage leading from the chamber 8| to the atmosphere, and opening the passage I0| leading from the source of fluid compressed by the compressor to the chamber 8|. Fluid under pressure thereupon flows to the chamber 8|, and therefrom tothe cylinder 30 associated,

with the unloading means and urging the piston 3| and the flngers 32 and 33 downwardly to force the valve discs 22 and 23 away from the valve seat 2I. This removes all load from the compressor andallows it to run idle so that the loads on the hearings will be at a minimum at a time when the pressure lubricating system is inoperative.

The inlet valve will be held in the open position as long as the pressure in the lubricating system remains at the low value, but as soon as the pressure in the lubricating system is restored to its proper value the pressure in the cylinder I20 will increase and the piston I 2| will be moved to the left, as viewed in Figure 3, to shift the valve element 83 to a position to cut oil the supply of fluid under pressure to the unloading control the unloading means in response to an, increase in the pressure of the fluid compressed by the compressor above a predetermined value so that the compressor is unloaded at a time when the pressure of the fluid in the reservoir has reached a predetermined value. It will be seen that the control valve device has a chamber I00 which is in communication with the passage IM and is thus subject to the fluid compressed by the compressor, and, on a predetermined increase in the pressure of the fluid in this chamber, the diaphragm I03 is urged tothe right against the pressure of the spring III. The pin I01 thereupon engages the valve disc I33 to urge this disc to the right away from its seat.

The valve disc I33, however, is urged to its seat by the pressure of the lubricant on the face of the disc and by the pressure of the spring I35 actingon the piston I32, and the pressure of the fluid in the chamber I00 must build up to a value great enough to overcome these forces as well as the force exerted by the spring I before the valve disc I33 will be forced away from its seat. As soon as the valve disc I33 is moved out of engagement with the seat I34,- the lubricant in the chamber I30 escapes to the chamber I40 and the pressure of the lubricant on the valve disc I33 is reduced, and, as the only force opposing movement of the diaphragm I03 is the spring I and the spring I35, the diaphragm I03 will move to the right very rapidly, thereby moving the valve disc I33 to the full open position. This permits lubricant to flow from the passage I23 to the chamber I30 and to the chamber I40 and therefrom to thepassage I to the piston chamber I20 on the left side of the piston I2| and out through the passage 82 to the crankcase. This quickly releases the pressure on the piston |2I and permits it to be moved very rapidly to the right by the spring 81, which shifts the valve element 83 to the right so that the chamber 8| is cut oil! from the atmosphere and is in communication with the fluid compressed by the compressor- This causes the unloading means to operate to hold the inlet valve open.

The valve disc I33 is held in the open position until the pressure in the chamber I00, which pressure is the same as that in the reservoir 88, drops to a value low enough that the springs I35 and III overcome the force on the diaphragm I03. This pressure will be somewhat lower than .that required to unseat the valve disc I33 bepressure of the lubricant in the chamber I30 will rise due to the decrease in the size of the opening controlled by the disc I33, and the pressure.

of the lubricant acting on the valve disc I33 will move-this disc to its seat very quickly when it once approachesits seat. The flow of fluid from the passage I23, therefore, will be cut off very quickly and the pressure of the fluid in the pis-- ton chamber I20 will" build up and the piston |2| will be forced to the left to move the valve element 83 to the left to cut'ofl communication between the chamber 3| and the passage 81, and

to permit communication between the chamber 8| and the atmosphere through the passage 82.

The movement of the. valve element 83 will be -.';very rapid due to the rapid increase of the presas pointed out above, results from the quick seating of the valve disc I33.

Rapid movement 01 the valve element Sibetween the position in which it closes communication between the chamber 8| and the source of fluid under pressure, and the position in which it closes communication between the chamber BI and the atmosphere, is desirable asthis prevents the loss of fluid under pressure through the chamber 8| which would take place if the valve element 93 moved slowly or was held in an inpressure of the lubricant will increase as the speed of the compressor increases, and when this p essure increases to a predetermined value, the piston I2! will be moved tothe left, thereby torcing the valve element 98 to the left so as to cut off communication between the chamber 88 and the pipe 31 and opening communication between the pipe 31 and the atmosphere to release the fluid in the unloading means and effect loading or the compressor, The compressor, therefore, is unloaded in starting until it has reacheda predetermined speed.

From the foregoing it will be seen-that I have provided control means adapted to control the unloading means associated with an air compressor to operate the unloading means to hold the inlet valve of the compressor open, and that this means is operable in response to a predetermined increase in the pressure or the fluid compressed by the compressor or to a failure or the lubricating system so that the compressor cannot be operated under load when it is not properly lubricated.

It will be seen also that the control device pro- ,vided by my invention has a lubricant discharge passage associated therewith and communicating with the compressor at a point vertically above the highest point of the compressor which is supplied with lubricant under pressure by the lubricating system so that in the event that there is a deficiency of lubricant, the lubricant supplied by the pump will be furnished to the operating parts of the compressor rather than to the con- .trol device.

In addition it will be seen that means is provided to limit the amounto! lubricant supplied to the control device so that only a portion of the lubricant pumped by the pump can escape through the control device when'this device is held in the open position 'as a result of an increase in the pressure of the fluid compressed by the compressor above the predetermined value.

While one embodiment of the improved control device provided by my invention has been 11- lustrated and described in detail, it should be understood that the invention is not limited to these details of construction, and that numerous changes and modifications may be made without departing from the scope of the following-claims.

Having now described my invention what I claim as new and desire to secure by Letters Patent, is:

When'the compressor is started, the

'sure of the fluid in the piston chamber I20, which,

1. In a fluid compressor, a lubricating system adapted to supply lubricant under pressure to portions of the compressor, means for unloading the compressor, control means responsive to the pressure of lubricant supplied thereto and operable to control said unloading means, and means responsive to the pressure of fluid compressed by the compressor and controlling the pressure of the lubricant supplied to the control means, said means comprising a valve element controlling a passage leading from said control means, said valve element being subject to the pressure of the lubricant supplied to the control means andbeing urged thereby to a position to close the passage controlled thereby.

' 2. In a fluid compressor, a lubricating system adapted to supply lubricant under pressure to portions of the compressor, means for unloading the compressor, and means to control the operation of said unloading means, said means comprising a first movable abutment subject to the pressure of the lubricant in the lubricating system, a second movable abutment subject to the pressure or fiuidpompressed by the compressor,- and a valve element controlling a passage leading from the lubricating system to control the pressure of the lubricant supplied to the first abutment, said valve element being movable by said second abutment to a position to open said passage, the valve element being subject to the pressure of the lubricant in the passage controlled thereby, movement of the valve element to the open position being opposed by the pressure of the lubricant in the passage controlled by the valve element, the means for unloading the compressor being controlled by movement of the first abutment.

3. In a fluid compressor, a lubricating system adapted to supply lubricant under pressure to portions of thecompressor, means for unloading thei compressor, fluid pressure responsive means to control said unloading means, and a control valve device adapted to control the supply of fluid under pressure to said fluid pressure responsive means, the control valve device comprising a valve element controlling the supply of fluid under pressure to the fluid pressure responsive means, a first movable abutment subject to the pressure of the lubricant in the lubricating system and controlling said valve element, and a second movable abutment subject valve controlling the supply of fluid under pressure to said fluid pressure responsive means, said valve-comprising a valve element having biasing means associated therewith and normally urging said valve element to the open position, a

movable abutment subject to the pressure of the lubricant in said lubricating system and operable in response to pressure above a predetermined 1 value to urge said valve element to the closed position; and means responsive to the pressure of the fluid compressed by the compressor and controlling the pressure of the lubricant operating on said abutment.

5. In a fluid compressor, a lubricating system adapted to supply fluid under pressure to portions or the compressor, means for unloading the 7 means, said control valve device having a chamber therein communicating with said fluid pressure responsive means, a first passage communi-' cating with said chamber and with a supply of fluid under pressure, a second passage communieating with said chamber and-with the atmosphere, valve means controlling each of said passages, a movable abutment subject to the pressure oi the lubricant in the lubricating system and operable in response to pressures above a predetermined value to move said valve means to a position to close one 01!, said passages and to open the other of said passages, and means responsive to the pressure of fluid compressed by the compressor and controlling the pressure of the lubricant supplied to the said abutment.

6. In a fluid compressor, a lubricating system adapted'to supply fluid under pressure to portions of the compressor, means for unloading the compressor, means responsive to fluid pressure and controlling said unloading means, and a control valve device controlling the supply of fluidunder pressure to said fluid pressure responsive means, said control valve device comprising a pair of movable abutments, one of said abutments being subject to the pressure of lubricant in the lubricating system, the second abutment being subject to the pressure of fluid compressed by the compressor, valve means controlling the supply of fluid to the unloading means, said valve means being controlled by said first abutment, and means controlled by the second abutment and controlling the pressure of lubricant supplied to the first abutment.

7. In a fluid compressor, a lubricating system adapted to supply fluid under pressure to portions of the compressor, means for unloading the compressor, means responsive to fluid pressure and controlling said unloading means, and a control valve device controlling the supply of fluid under pressure to said fluid pressure responsive means, the control valve device comprising a chamber communicating with the fluid pressure responsive means, a first passage communicating with said chamber and with fluid compressed by the compressor, a second passage communicating with said chamber and with the atmosphere, each of said passages having valve means associated therewith, said valve means comprising a valve element having biasing means associated therewith and operable to urge said valve element to a position to open the first passage and close the second passage, a first movable abutment subject to the pressure of fluid in the lubricating system and operable responsive to pressures above a predetermined value to move said valve element to a position to close said first passage and open said second passage, and a second movable abutment subject to the pressure of fluid compressed by the compressor and controlling the pressure of the lubricant supplied to the first abutment.

8. In a fluid compressor, a lubricating system adapted to supply lubricant under pressure to portions of the compressor, means for unloading the compressor, means responsive to fluid pres- Y sure and controlling said unloading means, and

a valve device controlling the supply of fluid under pressure to said fluid pressure responsive means, saidvalve device comprising a valve element having biasing means associated therewith and normally urging said valve element to the open position, a movable abutment subject to the pressure of the lubricant in said lubricating system and operable in response to pressure above a predetermined value to urge said valve element to the closed position, and means responsive to the pressure of the fluid compressed by the com pressor and controlling the pressure of the lubricant supplied to said abutment, said means comprising a valve element controlling a discharge passage associated with the lubricating system, said valve element being normally urged by the pressure of the lubricant in the lubricating system to a position to close said passage.

9. In a fluid compressor, a lubricating system adapted to supply lubricant under pressure to portions of the compressor, means for unloading the compressor, means responsive to fluid pressure and controlling said unloading means, and a valve device controlling the supply of fluid under pressure to said fluid pressure responsive means, said valve device comprising a valve element having biasing means associated therewith .and normally urging said valve element to the the pressure of the fluid compressed by the compressor and controlling the pressure of the lubricant supplied tosaidabutment, said means comprising a discharge passage leading from a portion of said lubricating system and a valve element controlling said passage, the discharge end of said passage being located vertically above the portions of the compressor supplied by lubricant under pressure from said lubricating system.

10. In a fluid compressor, a lubricating system adapted to supply lubricant under pressure to portions of the compressor, means for unloading the compressor, means responsive to fluid pressure and controlling said unloading means, and a control valve device controlling the supply of fluid under pressure to said fluid pressure responsive means, said control valve device, comprising a valve element having biasing means associated therewith and normally urging said element to the open position, a movable abutment subject to the pressure of the lubricant in said lubricating system, and operable in response to pressure above a predetermined value to urge said valve element to the closed position, means responsive to the pressure of the fluid compressed pressure to the compressor, means for unloading the compressor, control means operable by the pressure of lubricant supplied thereto for operating said unloading means, means to limit the rate 01 flow of lubricant from the lubricating system to said control means and'means responsive to the pressure of fluid compressed by the compressor for controlling the pressure of the lubricant applied to said control means.

12; In combination, a.- fluid compressor, a lubricating system adapted to supply lubricant under pressure to the compressor, means for unloading the compressor, control means operable by the pressure of the lubricant supplied thereto for operating said unloading means, valve means for controlling the pressure of the lubricant supplied to the control means, said valve means being operative upon a predetermined increase in the pressure of the fluid compressed to open the passage controlled thereby and reduce the pressure of the lubricant supplied to the control means, and means for preventing the movement of the said valve means to close said communication until the pressure of the fluid compressed has been reduced substantially below the pressure at which the valve means is moved to the open position.

13. In combination, a fluid compressor, a lubricating system adapted to supply lubricant under pressure-to the compressor, means for unloading the compressor, control means operable by the pressure of the lubricant supplied thereto for operating said unloading means, means to limit the rate of flow of lubricant to said control means, valve means for controlling the pressure of the lubricant supplied to the control means, said valve means being operated upon a predetermined increase in the pressure of the fluid compressed to open the passage controlled thereby and reduce the pressure of the lubricant supplied to the control means, and means for preventing the movement of the said valve means to close said passage until the pressure of the fluid compressed has been reduced substantially below the pressure at which the valve means is moved to the open position.

14. In combination, a fluid compressor, a lubricating system adapted to supply lubricant under pressure to the compressor, means for unloading the compressor, control means operable by the pressure of the lubricant supplied thereto for operating said unloading means, and valve means responsive to the pressure of the fluid compressed by the compressor and controlling a passage having a discharge end located vertically above the portions of the compressor supplied with lubricant by the lubricating system and through which fluid supplied to the control means is discharged whereby the pressure of the fluid supplied to the control means may be controlled.

15. In combination, a fluid compressor, a lubricating system adapted to supply lubricant under pressure to the compressor, means for unloading the compressor, control means operable by the pressure of the lubricant supplied thereto for operating said unloading means, means to limit the rate of flow of lubricant to the control means, and valve means responsive to the pressure of the fluid compressed by the compressor and controlling a passage having a discharge end located vertically above the portions of the compressor supplied with lubricant by the lubricating system and through which fluid supplied to the control means is discharged whereby the pressure of the fluid supplied to the control means may be controlled 16. In combination, a fluid compressor, a lubricating system adapted to supply lubricant under pressure to said compressor, means for unloading the compressor, means subject to and operated on a predetermined increase in the pressure of the fluid in a chamber to condition the unloading means to load the compressor, means for supplying lubricant from the compressor lubricating system to said chamber at a given rate, and

means subject to the opposing pressures of the fluid compressed by the compressor and of thefluid'in said chamber and controlling a communication through which fluid may bereleased from said chamber at a rate more rapid than said given rate.

17. In combination, a fluid compressor, a lubrieating system adapted to supply lubricant under pressure to said compressor, means for unloading the compressor, means subject to and operated on a predetermined increase in the pressure of the fluid in a chamber to condition the unloading means to load the compressor, means for supplying lubricant from the compressor lubricating system to said chamber at a given rate, a valve controlling a passage through which fluid may be released from said chamber at a rate more rapid than said given rate, a member subject to the opposing forces of a spring and of the pressure of the fluid compressed by the compressor for moving said valve to a position to open said passage, and means subject to the pressure of the fluid in said chamber and opposing operation of said member to move the valve to the position to open said passage.

18. In combination, a fluid compressor, a inbricating system adapted to supply lubricant under pressure to said compressor, unloading means operated on an increase in the pressure of the fluid supplied thereto to unload the compressor, valve means. controlling the supply of fluid under pressure to and the release or fluid under pressure from said unloading means, biasing means yieldingly urging the valve means to a position to supply fluid to said unloading means, movable abutment means subject to and operated on a predetermined increase in the pressure of the fluid in a chamber to move the valve means to a position to release fluid under pressure from said unloading means, means for supplying lubricant from the compressor. lubricating system to said chamber at a given rate, and means subject to the opposing pressure of the fluid compressed by the compressor and of the fluid in said chamber and controlling a communication through which fluid may be released from said chamber at a rate more rapid than said given rate. 19. In combination, afluid compressor, means for unloading the compressor, a pump driven in accordance with the speed 01' the compressor, means subject to and operated on a predetermined increase in the pressure of the fluid in a chamber to condition the unloading means to load the compressor, means for supplying to said chamber at a given rate fluid pumped by said pump, and means subject to the opposing pressures of the fluid in said chamber and of the fluid compressed by the compressor and controlling a communication through which fluid may be released from said chamber. a

20. In combination, a fluid compressor, means for unloading the compressor, a liquid circulating system operated in accordance with the speed of the compressor, means subject to and operated on a predetermined increase in the pressure 01' the fluid in a chamber to condition the unloading means to load the compressor, means for supplying liquid from said liquid circulating system to said chamber at a given rate, and meanssubject to the opposing pressures of the fluid compressed by the compressor and of the fluid in said chamher and controlling a communication through which fluid may be released from said chamber at a rate more rapid than said given rate.

21. In combination, a fluid compressor, a liquid circulating system operated in accordance with the speed of the compressor, unloading means operated on an increase in the pressure of the fluid supplied thereto to unload the compressor,

valve means controlling the supply of fluid under pressure to and the release of fluid under pressure from said unloading means, biasing means yieldingly urging the valve means to a position to supply fluid under pressure to the unloading means, means subject to and operated on a predetermined increase in the pressure of the fluid in a chamber to move the valve means to a position to release fluid under pressure from said unloading means, means for supplying liquid from said liquid circulating system to said cham-' her at a given rate, and means subject to the opposing pressures of the fluid in said chamber and of the fluid compressed by the compressor and controlling a. communication through which fluid CERTIFICATE OF colmsc'rion.

Patent No. 2,065,204. December 22, 1936.

BURTON S. AIKMAN..

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, second column, line 69, claim 11, for the word ."applied" read supplied; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 6th day of April A. D. 1937.

Henry Van Arsdale (Seal) Acting Commissioner of Patents. 

